We have theoretically investigated the properties of electronic transport in graphene heterostructures, which are consisted of two different graphene superlattices with one-dimensional periodic potentials. It is found that such heterostructures posse
ss an unusual tunneling state occurring inside the original forbidden gaps, and the electronic conductance is greatly enhanced and Fano factor is strongly suppressed near the energy of the tunneling state. Finally we present the matching condition of the impedance of the pseudospin wave for occuring the tunneling state by using the Bloch-wave expansion method.
